ByPeter Svensson, Associated PressMarch 7, 2012

Grant Beacon Middle School student, Jeriah Garcia, 13, works out an algebra problem on his school-supplied iPad in class at Grant, Colo. Apple is expected to reveal a new iPad HD on Wednesday, March 7, 2012, a device with a sharper screen, a faster processor and an option for faster wireless broadband.

NEW YORK — Apple is holding an event Wednesday in San Francisco, and has hinted that it will reveal a new iPad model. Rumors speak of an updated tablet with a speedier processor, a sharper screen, and a new iPad HD name.

If last year's launch of the iPad 2 is any guide, the new iPad model will go on sale in the U.S. next week, likely on Friday.

The upgrade from the iPad 2 to the iPad HD will be less significant than the upgrade from the original iPad to the iPad 2, which added two cameras while cutting both the thickness and the weight of the device.

Another big question is whether Apple will reveal its rumored foray into making TV sets. Some have speculated that the invite to the Apple event, which said "We have something you really have to see," points in that direction.

Apple already sells and "Apple TV." It's not a TV, but a small box that attaches to a television set to display movies and play music from iTunes.

The iPad launch comes as Apple has reached a rare milestone: Last week, it was worth more than $500 billion. Only six other U.S. companies have been worth that much, and none have held that valuation for long. On Tuesday, Apple's stock fell, bringing its market value down to $493 billion, but analysts believe the company is worth closer to $550 billion.

These are some rumored features of the iPad HD:

— A sharper screen, similar to the "Retina Display" on the iPhone 4 and 4s. The rumored resolution is 2048 by 1536 pixels, which would make text look smoother and some high-resolution pictures look better. It won't make much of a difference for images on the Web, or video.

Some speculate that Apple will call the model the "iPad HD," for "high definition," rather than "iPad 3."

— The new iPad could include Siri, the voice-activated "assistant" found on the iPhone 4S. Siri has gotten mixed reviews, but Apple has been touting the feature heavily in its advertising, and it would make sense to expand the availability of this high-profile feature.

— Faster wireless capabilities. IPads are available with built-in modems for AT&T's and Verizon's third-generation, or "3G" cellular networks in the U.S. The iPad 3 could come in a version that offers faster "4G" or "LTE" networks. However, most iPads are used only on Wi-Fi, so an "LTE" chip wouldn't matter to most buyers.

In this respect, Apple is playing catch-up. Some competitors, such as Samsung and Motorola, already sell LTE-compatible tablets.

Since last fall, Sprint Nextel Corp. has sold the iPhone. But it doesn't sell the iPad. It's possible it could join AT&T and Verizon Wireless in selling the iPad 3.

— A faster processor. This is pretty much a given, since every new iPhone or iPad has improved on the computing power of its predecessor. But few users complain about their iPads being slow, so this should not be a major selling point.

Sarah Rotman Epps, an analyst for Forrester Research, said hardware features aren't that important to tablet buyers.

"It's about the services — what you can do with the device," she said in a blog post.

Apple's competitors have slowly come to realize this, but only after bringing out dozens of tablets with whiz-bang features like 3-D cameras. The competitor that's done the best is Amazon.com Inc. Its Kindle Fire tablet is cheaper than the iPad, but what really sets it apart is that it's tied into Amazon's book, movie and music stores, making it an easy route to entertainment, just like the iPad.

Still the Kindle Fire has a long way to go. Epps estimates that Amazon sold 5.5 million Kindle Fires in the fourth quarter of last year. Meanwhile, Apple sold 15.4 million iPads, and has sold 55.3 million in total.